Firefox Quantum you’re hearing about? What is that? It is a rewrite of Firefox that is touted to be faster and more resource efficient.
20180716/DuckDuckGo firefox quantum release
20180716/https://blog.mozilla.org/blog/2017/11/14/introducing-firefox-quantum/
Okay, they say that… but I doubt the resource consumption is down to what we’ve observed in the earlier versions. Modern Firefox probably still uses a lot of resources.